Electrons on a sphere in disorder potential

We investigate, both analytically and numerically, the behavior of the electron gas on a sphere in the presence of point-like impurities. We find a criterion when the disorder can be regarded as small one and the main effect is the broadening of rotational multiplets. In the latter regime the statistics of one impurity-induced band is studied numerically. The energy level spacing distribution function follows the law P(s) ~ s exp(-a s^b) with 1<b<2. The number variance shows various possibilities, strongly dependent on the chosen model of disorder.Comment: 11 pages, REVTEX, 9 eps figures; references added to Sec.

REVEALED COMPARATIVE ADVANTAGE AND THE MEASUREMENT OF INTERNATIONAL COMPETITIVENESS FOR AGRICULTURAL COMMODITIES: AN EMPIRICAL ANALYSIS OF WOOL EXPORTERS

Trade liberalization and laissez-faire economics are altering the structure of agricultural production and trade. The principle of comparative advantage, a classic tenet of economics, is a useful tool for understanding the future of world agriculture. This study employs a "Revealed Comparative Advantage" approach to investigate patterns of comparative advantage among six major wool exporting countries.International Relations/Trade,

Ignorance is Almost Bliss: Near-Optimal Stochastic Matching With Few Queries

The stochastic matching problem deals with finding a maximum matching in a graph whose edges are unknown but can be accessed via queries. This is a special case of stochastic $k$-set packing, where the problem is to find a maximum packing of sets, each of which exists with some probability. In this paper, we provide edge and set query algorithms for these two problems, respectively, that provably achieve some fraction of the omniscient optimal solution. Our main theoretical result for the stochastic matching (i.e., $2$-set packing) problem is the design of an \emph{adaptive} algorithm that queries only a constant number of edges per vertex and achieves a $(1-\epsilon)$ fraction of the omniscient optimal solution, for an arbitrarily small $\epsilon>0$. Moreover, this adaptive algorithm performs the queries in only a constant number of rounds. We complement this result with a \emph{non-adaptive} (i.e., one round of queries) algorithm that achieves a $(0.5 - \epsilon)$ fraction of the omniscient optimum. We also extend both our results to stochastic $k$-set packing by designing an adaptive algorithm that achieves a $(\frac{2}{k} - \epsilon)$ fraction of the omniscient optimal solution, again with only $O(1)$ queries per element. This guarantee is close to the best known polynomial-time approximation ratio of $\frac{3}{k+1} -\epsilon$ for the \emph{deterministic} $k$-set packing problem [Furer and Yu, 2013] We empirically explore the application of (adaptations of) these algorithms to the kidney exchange problem, where patients with end-stage renal failure swap willing but incompatible donors. We show on both generated data and on real data from the first 169 match runs of the UNOS nationwide kidney exchange that even a very small number of non-adaptive edge queries per vertex results in large gains in expected successful matches

The Development Of Wave Power: A Techno-Economic Study

A study of the development of wave power was undertaken by the National Engineering Laboratory for the Department of Energy and was presented in a two-part report (Summary and Full Report) dated February 1975. Because of the interest generated in the development of wave power it was decided to make the NEL contribution generally available in this report which presents in one document the bulk of the material in the two-part report. The text has not been revised to take account of developments which have taken place since February 1975 and it should be emphasised that this report represents the status and NEL's thinking on wave power at that time. Some footnotes have been added to indicate where new information is in conflict with that in the report. No attempt has been made to take account of all new information in this way

Modelling of Trailing Edge Separation on Arbitary Two-Dimensional Aerofoils in Incompressible Flow Using an Inviscid Flow Algorithm. G.U. Aero Report 8202

An algorithm for estimating the lift, moment and pressure distribution on arbitary two dimensional aerofoils in incompressible flow is presented. The procedure uses an inviscid analysis of the physics of the real flow, which invokes the application of a linear vortex panel model. The separated wake geometry is determined iteratively, starting from an initial assumption. A boundary layer analysis is not performed, hence the upper surface separation point is a necessary input to the algorithm. Lower surface separation is assumed to occur at the trailing edge. A selection of results and comparison with experimental data is presented. The scatter in the calculated and experimental data values is attributed mainly to the lack of boundary layer displacement and compressibility effects. A fortran code listing of the algorithm is given in the Appendix

Modelling of Trailing Edge Separation on Arbitary Two-Dimensional Aerofoils in Incompressible Flow Using an Inviscid Flow Algorithm. G.U. Aero Report 8202

An algorithm for estimating the lift, moment and pressure distribution on arbitary two dimensional aerofoils in incompressible flow is presented. The procedure uses an inviscid analysis of the physics of the real flow, which invokes the application of a linear vortex panel model. The separated wake geometry is determined iteratively, starting from an initial assumption. A boundary layer analysis is not performed, hence the upper surface separation point is a necessary input to the algorithm. Lower surface separation is assumed to occur at the trailing edge. A selection of results and comparison with experimental data is presented. The scatter in the calculated and experimental data values is attributed mainly to the lack of boundary layer displacement and compressibility effects. A fortran code listing of the algorithm is given in the Appendix

Large scale prop-fan structural design study. Volume 1: Initial concepts

In recent years, considerable attention has been directed toward improving aircraft fuel consumption. Studies have shown that the inherent efficiency advantage that turboprop propulsion systems have demonstrated at lower cruise speeds may now be extended to the higher speeds of today's turbofan and turbojet-powered aircraft. To achieve this goal, new propeller designs will require features such as thin, high speed airfoils and aerodynamic sweep, features currently found only in wing designs for high speed aircraft. This is Volume 1 of a 2 volume study to establish structural concepts for such advanced propeller blades, to define their structural properties, to identify any new design, analysis, or fabrication techniques which were required, and to determine the structural tradeoffs involved with several blade shapes selected primarily on the basis of aero/acoustic design considerations. The feasibility of fabricating and testing dynamically scaled models of these blades for aeroelastic testing was also established. The preliminary design of a blade suitable for flight use in a testbed advanced turboprop was conducted and is described in Volume 2

SPARC Controls Melanoma Cell Plasticity through Rac1.

Cell transition to a more aggressive mesenchymal-like phenotype is a hallmark of cancer progression that involves different steps and requires tightly regulated cell plasticity. SPARC (Secreted Protein Acidic and Rich in Cysteine) is a matricellular protein that promotes this transition in various malignant cell types, including melanoma cells. We found that suppression of SPARC expression in human melanoma cells compromised cell migration, adhesion, cytoskeleton structure, and cell size. These changes involved the Akt/mTOR pathway. Re-expression of SPARC or protein addition restored all the cell features. Suppression of SPARC expression was associated with increased Rac1-GTP levels and its membrane localization. Expression of the dominant negative mutant of Rac1 counteracted almost all the changes observed in SPARC-deficient cells. Overall, these data suggest that most of the SPARC-mediated effects occurred mainly through the blockade of Rac1 activity.Fil: Salvatierra Colussi, Edgardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Alvarez, Mariano J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Leishman, Claudia C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Rivas Baquero, Elvia Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Lutzky, Viviana P.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Estudios Farmacológicos y Botánicos. Universidad de Buenos Aires. Facultad de Medicina. Centro de Estudios Farmacológicos y Botánicos; Argentina. The Royal Brisbane Hospital; AustraliaFil: Chuluyan, Hector Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Centro de Estudios Farmacológicos y Botánicos. Universidad de Buenos Aires. Facultad de Medicina. Centro de Estudios Farmacológicos y Botánicos; ArgentinaFil: Podhajcer, Osvaldo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentin

Structural Transition Kinetics and Activated Behavior in the Superconducting Vortex Lattice

Using small-angle neutron scattering, we investigated the behavior of a metastable vortex lattice state in MgB2 as it is driven towards equilibrium by an AC magnetic field. This shows an activated behavior, where the AC field amplitude and cycle count are equivalent to, respectively, an effective "temperature" and "time". The activation barrier increases as the metastable state is suppressed, corresponding to an aging of the vortex lattice. Furthermore, we find a cross-over from a partial to a complete suppression of metastable domains depending on the AC field amplitude, which may empirically be described by a single free parameter. This represents a novel kind of collective vortex behavior, most likely governed by the nucleation and growth of equilibrium vortex lattice domains.Comment: 5 pages plus 3 pages of supplemental materia